68 HEMOGLOBIN 



Nowadays neither the method used by Peters nor that used by 

 Bum would be employed, the calibration of the apparatus being 

 carried out by some form of the method described by Hoffmann (16). 

 There is of course quite a literature on the subject as the differential 

 gas apparatus has come into general use for many types of respiratory 

 work. A very convenient method of calibration is that described by 

 Miinzer and Neumann (17), and quoted in Ludwig Pincussen's book (18), 

 but that is a digression. Looking back from the distance of fifteen 

 years there are several points which deserve a word of comment. 



(1) By separating the corpuscles from the plasma and discarding 

 the latter, Peters' results stand free of the principal criticism to which 

 the use of ferricyanide in the differential apparatus has been subjected, 

 namely, that of a too low oxygen reading caused by auto-oxidation 

 of the ferricyanide by the lipoids in the plasma. 



(2) Peters' figures are certainly not above 401. Bayliss(i9) put 

 forward the suggestion that the haemoglobin in these and similar 

 experiments was not really saturated, and that if exposed to a greater 

 concentration of oxygen, it would unite with more of that gas. 



Subsequent work has failed to bear out Bayliss' contention. I tested 

 the matter with the following result (19). I exposed blood to a gaseous 

 mixture of 85 per cent, oxygen and 15 per cent, nitrogen, and found 

 the following percentage degrees of saturation as compared with that 

 regarded as complete: 102, 99, 98 and 97 in four experiments. These 

 values were corrected for the gas physically dissolved, and pointed 

 to a true saturation point. 



W. E. L. Brown (20) also approached it in another way; he argued 

 thus. Carbon monoxide has, say, 250 times the affinity for haemoglobin 

 that oxygen has (more or less according to the haemoglobin in ques- 

 tion). An exposure to 1 atmosphere of CO should then saturate 

 the haemoglobin to the same degree as exposure to 250 atmospheres 

 of oxgyen, or exposure to I atmosphere of CO should have an effect 

 quantitatively equal to 250 atmospheres of air. Brown, however, 

 found that when blood which had been equilibrated with oxygen 

 in air was exposed to carbon monoxide, the quantity of carbon 

 monoxide taken up was neither greater nor less than that of the 

 oxygen which was given out. It would appear then that aerated 

 blood did not fall short of saturation with oxygen, by any measurable 

 quantity. Peters' results are justified of criticism on that point. 



(3) Granting that his results are not above 401, are they below it? 

 and if so, why? Already it has been stated (a) that as given by Peters 



